In this project it is proposed to study the synthesis of the first component of complement (Cl) in vitro by cells derived from colonic and transitional cell carcinomas. The object will be to establish lines of cells which retain this ability as one of their stable biochemical markers. In addition to examining the molecular parameters of synthesis of Cl, and/or its subunits Clq, Clr, and Cls. by such cells, it is proposed to purify the new synthesized proteins by affinity chromatography and determine their structural relationship to the comparable protein isolated from serum. Finally, it is proposed to map the actual as well as potential sites of synthesis in humans of CL in normal and cancer states, according to the ability of the excised cells to make Cl in vitro in primary cultures.